Patent GB-828785-A (GB)
Title: Control apparatus for aircraft
Inventor: SUMMERLIN FREDERICK ARTHUR
IPC: B64C13/24
Filed: 1957-09-27
Abstract: 828,785. Fluid-pressure servomotor-control systems. SPERRY GYROSCOPE CO. Ltd. Sept. 27, 1957, No. 30435/57. Class 135. [Also in Group XXXIII] Aircraft control apparatus comprises a control surface in a number of independently movable portions, each having its own main actuator and control means therefor, and an auxiliary actuator arranged during an automatic mode of operation of apply an input signal derived from an instrument to the control means of one only of the main actuators, a connection from the output of this main actuator being arranged during the automatic mode of operation to apply to the other main actuators an input signal corresponding to that applied to the one main actuator. Fig. 1 shows a control surface in two parts 11, 12, each moved through linkwork 29 by a hydraulic actuator 13 or 14, the valve 15 or 16 of which is operated through a rod 28 containing a spring box 31 and pivoted to an intermediate point of a differential lever 18 or 19, this lever being pivoted at one end to a feed back rod 27 connected to the surface part, and pivoted at the other end to a common input rod 25 attached to a manual control 17 provided with a spring feel device 26. The surface parts 11, 12, are thus each maintained in a position corresponding to that of the manual control, rods 28 being re-centred after manual displacement by the feed-back rods 27. The connection between valve 16 and lever 19 contains a differential lever 33, one input to which is derived from an actuator 22 operated by an autopilot 21. During manual control, actuator 22 is not operative. During automatic control, an actuator 39 moves a lever 37 to engage a notch 36 with a boss 35 on a slider 35<SP>1</SP> carrying the pivot between lever 19 and rod 28 and thus holding this pivot stationary. The input to valve 16 is thus derived only from actuator 22. A positional feed-back signal is fed to the autopilot from a potentiometer 42 through a switch 43 closed only during automatic control. The movement of surface part 12 in response to the autopilot output is transmitted to the manual control 17 through feed-back rod 27, lever 19, and rod 25, the latter also operating the other surface part 11 through its actuator 13. A large force applied to boss 35 will raise notch 36, freeing rod 28 for manual control, and closing a switch 41 disabling the autopilot. Fig. 2 shows an alternative arrangement of the hydraulic control system. The hydraulic surface actuator cylinder 51 is pivoted to the aircraft at 52, and its piston rod 69 is pivoted to the surface at 53 and to the feed-back rod 27 at 54. The differential lever 18 is pivoted at one end to the input rod 25 and at its other end is pivoted together with one end of a lever 46 to the feed-back rod 27 at 70. The other end 71 of lever 46 is urged into alignment with lever 18 by two stiff cantilever springs 61 secured to lever 18 near pivot 70 and bearing on levers 18 and 46 at 72, 73. The end 71 of lever 46 is pivoted to the input lever 47 of the actuator valve 15. A pin 59 on lever 18 slides in a guide slot 58 in lever 46. Normally, levers 18 and 46 remain aligned, but should the actuator valve stick, lever 18 can still be moved, flexing springs 61, allowing rod 25 and the other actuators to be operated. The spring boxes 31, Fig. 1, fulfil a similar function. The actuator 39 and lever 37, Fig. 2, are mounted on the actuator cylinder 51. Specification 828,786 is referred to.